This invention relates to a seal for a rotating shaft. More particularly the invention defines a seal for an engine crankshaft application.
Seals of the type of the present invention are used to provide a fluid seal between a rotating shaft and the housing in which the shaft is located. The seal is normally used to retain fluid in the housing. The fluid is frequently a lubricant, such as oil, that is used to provide lubrication for the rotating shaft and other moving components within the housing. The fluid is often under pressure or being moved within the housing by a pump or the forces generated by the rotating shaft.
To provide an adequate fluid seal, the seal is positioned in engagement with the rotating shaft. A diaphragm is also frequently used as part of the fluid seal. The diaphragm extends from the seal face to the outer housing to complete the fluid seal between the outer housing and the rotating shaft.
During the rotation of the shaft the friction between the seal and the shaft can generate considerable heat. The heat can significantly reduce the life of the seal. The heat is also transferred directly to the diaphragm or elastomeric seal in these prior art seals. As the diaphragms are normally made of an elastomeric material this excess heat can significantly reduce the effectiveness and life of the diaphragm or elastomeric member. Accordingly, there is a need for a fluid seal that effectively deals with the heat generated by the engagement of the seal against the rotating shaft. Also, as the size of the shaft increases, the surface speed of the seal significantly increases. The increased surface speed of the seal results in an increase in the heat generated and the increased heat can drastically reduce the life of the seal.
Fluid seals of the present invention are usually used in connection with crankshafts for industrial engines. The design of the prior art seals do not resist the heat generated by high surface speeds of the seal or withstand the axial movement caused by the extreme loads placed on the crankshaft in large industrial engines. Such axial movement can produce stresses in the seal element or diaphragm that can significantly reduce the life of the seal or diaphragm. Accordingly, there is a need in the prior art for a fluid seal that can accommodate such axial movement without having a detrimental effect on the diaphragm.
The prior art seals have also had difficulty in providing an initial seal between the seal face and the rotating shaft. To provide an adequate initial seal, the prior art face seals have had to resort to expensive machining techniques, such as lapping to form a mating surface between the seal and mating face on the shaft. Such machining or lapping is very expensive and significantly increases the cost of the fluid seal. Accordingly, there is a need in the prior art to provide a fluid seal with good initial sealing properties at a reasonable cost. The need for such a seal becomes increasingly significant as the size of the seal increases.